Got a response. We will get more of my questions answered once his machinist returns.

i will get back to you in week or so when the machinist who made them is back from holidays

the front diffs were multi-plate with 2 different ramp angles. the breakaway torque and ramp angles could be varied depending on the application, so there is no such thing as one diff for all uses.

the last new one we had about 4 years ago was A$3200 from memory, but we would have to totally re-cost it, and the price will change based on quantity.

i cannot imagine a Toyota gearbox handling 800AWHP as were were busting them at half that value. even the Xtrac boxes were limited to about 500HP.

these diffs were successfully used in dozens or professional GpA rally cars here and the last one went into a S2000 prototype car. none of these cars made over 400hp, but thats not to say what the diff will handle. I will be able to calculate torque capacity if this inquiry progresses

So far we are just discussing diffs. Not sure if they do gearsets, but there are some that already exist. I imagine this is still going to be a costly option for most, but it will be a more viable option than the 6k diff currently made.

The TTA clutch type diff I posted earlier. They also make an active center LSD. I think its close to the 15k range now. If this company make theirs again, it is clutch type. Seems that has been the only ones actually ever made for our cars so far.